Lee, We are dealing with this same issue of bypass caps for BGAs. If we place the caps outside the shape of the BGA as you suggest, how much inductance is added by the planes over a distance of say 0.5" if the planes are spaced close together, say 5 mils. Thanks - Joel Lee Ritchey wrote: If you connect capacitors to pins with traces, the added inductance will degrade theri performance enough that they will likely be of little use. Better to place the capacitors outside the shape of the BGA and connect them into the planes directly with vias. No, they don't need to directly under the BGA as long as the planes are continuous. [Original Message] From: Dagmara Avanindra <dagmara.avanindra@xxxxxxxxx>[1] To: <subramanian1683@xxxxxxxxx>[2] Cc: <si-list@xxxxxxxxxxxxx>[3] Date: 5/12/20068:46:23 PM Subject: [SI-LIST] Re: Decoupling capacitors for BGA Subbu, if your board is not thick, you may want to consider using 0201 caps directly underneeth the BGA aray, especially if GND and VDD are located directly diagonally across from each other. If you connect caps via individual traces to the pins, you will get alot of resistivity. Which can bea plus if your goal is to dampen high-frequency noise. However, if you maketraces very thin and long, you may slow your response time too. So calculate your resisitivity per square to figure out what is the optimal cap connection for you. Dagmara On 5/12/06, Subramanian R <subramanian1683@xxxxxxxxx>[4] wrote: Hello All, We are using a 0.5mm Pitch 457-Pin BGA Processor. It is running at a maximum of 532MHz. It has 60 Power pins (Core &I/O) How do i place the Decoupling capacitors? Now we have placedall decaps (0402 pack) around the BGA (like an island) and connected itto the VCC plane. Should i need to route it to the individual pins itself? The BGA does not have much space between the Balls. So not more than 4-5 capscan be placed right over the BGA on the other side. The other thing i cango for is Inter-plane capacitance. But for that VCC-GND dielectric should be around 2-3mils, i understand. That doesn't look possible with our PCB thickness requirements. It is a 6-layer PCB Thanks for any suggestions. Regards Subbu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[5] with 'unsubscribe'in the Subject field or to administer your membership from a webpage, go to: //www.freelists.org/webpage/si-list[6] For help: si-list-request@xxxxxxxxxxxxx[7] with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ[8] List technical documents are available at: http://www.si-list.org[9] List archivesare viewable at: //www.freelists.org/archives/si-list[10] or at our remote archives: http://groups.yahoo.com/group/si-list/messages[11] Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu[12] ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[13] with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list[14] For help: si-list-request@xxxxxxxxxxxxx[15] with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ[16] Listtechnical documents are available at: http://www.si-list.org[17] List archives are viewable at: //www.freelists.org/archives/si-list[18] or atour remote archives: http://groups.yahoo.com/group/si-list/messages[19] Old(prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu[20] ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx[21] with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list[22] For help: si-list-request@xxxxxxxxxxxxx[23] with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ[24] Listtechnical documents are available at: http://www.si-list.org[25] List archives are viewable at: //www.freelists.org/archives/si-list[26] or atour remote archives: http://groups.yahoo.com/group/si-list/messages[27] Old(prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu[28] --- Links --- 1 mailto:dagmara.avanindra@xxxxxxxxx 2 mailto:subramanian1683@xxxxxxxxx 3 mailto:si-list@xxxxxxxxxxxxx 4 mailto:subramanian1683@xxxxxxxxx 5 mailto:si-list-request@xxxxxxxxxxxxx 6 //www.freelists.org/webpage/si-list 7 mailto:si-list-request@xxxxxxxxxxxxx 8 http://si-list.org/wiki/wiki.pl?Si-List_FAQ 9 http://www.si-list.org 10 //www.freelists.org/archives/si-list 11 http://groups.yahoo.com/group/si-list/messages 12 http://www.qsl.net/wb6tpu 13 mailto:si-list-request@xxxxxxxxxxxxx 14 //www.freelists.org/webpage/si-list 15 mailto:si-list-request@xxxxxxxxxxxxx 16 http://si-list.org/wiki/wiki.pl?Si-List_FAQ 17 http://www.si-list.org 18 //www.freelists.org/archives/si-list 19 http://groups.yahoo.com/group/si-list/messages 20 http://www.qsl.net/wb6tpu 21 mailto:si-list-request@xxxxxxxxxxxxx 22 //www.freelists.org/webpage/si-list 23 mailto:si-list-request@xxxxxxxxxxxxx 24 http://si-list.org/wiki/wiki.pl?Si-List_FAQ 25 http://www.si-list.org 26 //www.freelists.org/archives/si-list 27 http://groups.yahoo.com/group/si-list/messages 28 http://www.qsl.net/wb6tpu -- Binary/unsupported file stripped by Ecartis -- -- Type: text/x-vcard -- File: joel.vcf ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu